HomeMy WebLinkAboutCDP 16-27; TABATA RANCH LOT 3; DESIGN OF ALLAN BLOCK SEGMENTAL WALL; 2016-11-22ABIENGINEERING
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DESIGN OF
ALLAN BLOCK SEGMENTAL WALL
Tabata Family Trust - Lot 3
Strawberry Place
Carlsbad, California
DEC 0 52016
Prepared for:
Homeland Engineering, Inc.
11337 Moreno Avenue
Lakeside, California 92040
November 22, 2016
Project No. 16221
ABI Engineering Consultants, Inc.
1701 East Edinger Avenue, Suite A9
Santa Ana, California 92705
Tel: (888) 220-5596
Fax: (714) 866-4171
Allan Block Wall Design
Tabata Family Trust - Lot 3, Carlsbad, CA
TABLE OF CONTENTS
INTRODUCTION..........................................................................................................................1
PROPOSED WALL DESCRIPTION .......................................................................................... 1
DESIGN METHODOLOGY ........................................................................................................ 1
SEISMIC DESIGN METHOD ..................................................................................................... 1
DESIGNPARAMETERS ............................................................................................................. 1
SoilsParameters .........................................................................................................................1
WallParameters ......................................................................................................................... 1
ANALYSIS.....................................................................................................................................2
StaticAnalysis.............................................................................................................................2
SeismicAnalysis..........................................................................................................................2
RECOMMENDATIONS...............................................................................................................2
REFERENCES...............................................................................................................................2
ABI Engineering Consultants, Inc.
ABI Project No. 16221
Allan Block Wall Design
Tabata Family Trust - Lot 3, Carlsbad, CA
INTRODUCTION
This report presents the design parameters, design methodology, and calculations performed to design
proposed one segmental block retaining walls using Allan Block units at Tabata Family Trust - Lot 3,
Strawberry Place, Carlsbad, California. The proposed retaining wall will be utilized to create building pad.
PROPOSED WALL DESCRIPTION
Based on our review of the grading plan provided (Rancho Coastal), one Allan Block retaining wall is
proposed within the property. This wall is labelled as Allan Block Wall #1 for reference in this report. The
maximum height of the walls will be 7.00nft.
DESIGN METHODOLOGY
The computer code AB Walls 15 Version 15.1.5 developed by Allan Block Corporation is used for the design
of the wall. The computer code is based on the methods presented in National Concrete Masonry Association
guidelines (NCMA 2010). The NCMA method of design of segmental block walls uses Coulomb Earth
Pressure theory. AB Walls 15 program is customized for use with Allan Block and allows specifying choice
of block types and geogrids reinforcement. The results of the analysis are included as Appendix A. The
analysis was performed for different heights and surcharge conditions, as applicable.
SEISMIC DESIGN METHOD
The seismic internal stability of the Allan Block segmental wall is explored using AB Wall 15, which
incorporates pseudo-static rigid body approach that adopts the Mononobe-Okabe method to calculate dynamic
forces (NCMA 2010). A seismic acceleration coefficient of 0.32g is used in the seismic analysis.
DESIGN PARAMETERS
Soils Parameters
Based on the recommendations provided in the geotechnical report (Vinje & Middleton) the following soils
parameters are used for the design of the wall:
Reinforced Fill Retained Soils Foundation Soils
Internal Friction Angle, cb° 30 30 30
Cohesion, C (jsf) 0 0 0
Soil Unit Weight, y (pcf) 120 120 120
Wall Parameters
BLOCKS: 12-inch deep Allan Block Units weighing approximately 75 lbs each.
SURCHARGE: 2H: IV Backfill slope.
BATTER: 15 degrees to vertical.
EMBEDMENT: 0.5' or 10% of wall height (minimum).
GEOGRIDS: Design is based on Fortrac 35/20-20 manufactured by Huesker and Mirafi Miragrid 3XT
manufactured by TenCate. Equivalent or higher grade can be used. Other types of grids may be used upon
approval by the engineer.
The design of the retaining wall assumes no build up of hydrostatic pressures within the reinforced fill zone of
the wall. Therefore, construction of an effective subdrain system behind the reinforced soil zone is critical to
the performance of the wall. Any back-cut drain required shall be determined by the project geotechnical
engineer and shall be installed per the direction of the project geotechnical engineer.
ABI Engineering Consultants, Inc.
ABI Project No. 16221
Allan Block Wall Design
Tabata Family Trust - Lot 3, Carlsbad, CA
ANALYSIS
The wall design is based on the following factor of safety (FS) for stability analysis of the wall. The factors
of safety are for static loading conditions are indicated below and are based on the current standard of
practice.
Static Analysis
FSSljdjng = 1.50, FSsearing = 2.00, FSvertuming = 1.50, FSpuu.out = 1.50, and FSn ainties = 1.50
Seismic Analysis
FSsluding = 1. 13, FSaearing = 1.50, FSovemirning = 1.13, = 1. 13, and FSnajn = 1.13
The summary calculations present the data and results for each section of the wall.
RECOMMENDATIONS
The wall shall be constructed per the details and geogrid reinforcement schedule based on the design
calculations provided in this report, typical section, reinforcement schedule, and construction notes presented
on drawings. The Allan Block walls shall be constructed per the manufacturer's recommended procedures.
No substitution shall be allowed for blocks type or for the unit fill required within the units and behind the
blocks.
The foundation, retained, and backfill soils shall have the minimum shear strength properties as used for
design in this report. All backfill shall be placed in loose lifts not exceeding 8 inches, moisture conditioned,
and compacted to a minimum of 90% of the maximum dry density determined by Modified Proctor
compaction test (ASTM D1557). The compaction tests shall be performed on backfill soils for meeting the
minimum densities recommended. Any changes to foundation, retained and backfill soil properties and
loading conditions on the wall should be brought to our attention. The temporary excavation back-cut,
grading, ground improvement, fill settlement control, and sub-drain, and surface-drainage system for the
Allan Block walls shall be per the Project Soils and Civil Engineer's recommendations.
NCMA 2010, Design Manual for Segmental Retaining Walls, Third Edition, 2010.
Allan Block Engineering Manual, Allan Block Corporation.
Rancho Coastal Engineering & Surveying, Grading Plan, Tabata Family Trust - Lot 3, Strawberry
Place, Carlsbad, California, dated November 17, 2016.
Vinje & Middleton Engineering, Inc., Geotechnical Update Report and Grading Plan Review,
Proposed Tabata Ranch Subdivision, Lemon Leaf Drive, Carlsbad, California, dated August 2,
2006.
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ABI Project No. 16221
Allan Block Wall Design
Tabata Family Trust - Lot 3, Carlsbad, CA
APPENDIX A - Design Calculations
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ABl Project No. 16221